With the popularization of portable products such as mobile phones and notebook computers, the demand for lithium ion batteries is increasing. Lithium ion battery positive electrode material is the core material of lithium ion battery. Its performance and quality directly affect the important performances of lithium ion battery such as capacity, life, safety and DC resistance (DCR). The DCR of lithiumion battery has been the focus of attention in recent years. When the DCR of lithiumion battery is too large, even if the battery capacity is high, the voltage will drop rapidly and the mobile phone will automatically shut down. Therefore, reducing DCR of an electrode assembly is of great significance for lithium ion batteries.
Currently, the main means of reducing DCR is to reduce the particle size of lithium cobaltate (LCO) or to coat LCO with conventional Al2O3, TiO2, MgO and ZrO2. The DCR can be improved by reducing the particle size, increasing the specific surface area (BET), etc., but the particle size being too small and the BET being too large leads the compact density to be too low, resulting in a low volumetric energy density of the entire electrode assembly and impaired high-temperature storage performance. For coating with conventional Al2O3, TiO2, MgO, and ZrO2, although these coating methods can improve the lithium ion diffusion coefficient, the electron conductance is lowered due to the formed oxide coating layer being non-conductive, thus the improvement effect on DCR is limited.
In the prior art disclosed, coating a lithium cobaltate with a fast ion conductor may increase the lithium ion diffusion coefficient, thereby reducing DCR to some extent, but the electron conductance after coating will be reduced and the improvement effect will be not obvious.